Formation of CuSbS2 and CuSbSe2 thin films via chalcogenisation of Sb-Cu metal precursors

Due to the availability and low cost of the elements, the ternary Cu-Sb-S and Cu-Sb-Se semiconductor systems are being studied as sustainable alternative absorber materials to replace CuIn(Ga)(S,Se)2 in thin film photovoltaic applications. Simple evaporation of the metal precursors followed by annealing in a chalcogen environment has been employed in order to test the feasibility of converting stacked metallic layers into the desired compounds. Other samples have been produced from aqueous solutions by electrochemical methods that may be suitable for scale-up. It was found that the minimum temperature required for the complete conversion of the precursors into the ternary chalcogen is 350 C, while binary phase separation occurs at lower temperatures. The new materials have been characterised by structural, electrical and photoelectrochemical techniques in order to establish their potential as absorber layer materials for photovoltaic applications. The photoactive films consisting of CuSbS2 and CuSbSe2 exhibit band-gap energies of ~ 1.5 eV and ~ 1.2 eV respectively, fulfilling the Shockley-Queisser requirements for the efficient harvesting of the solar spectrum.